1. Field of Invention
The present invention relates to a method for making a micro-electro-mechanical system (MEMS) device, in particular to a method for making a MEMS device which is compatible to a standard CMOS process and can be easily integrated with post treatment processes such as surface micromachining or bulk micromachining.
2. Description of Related Art
MEMS devices are used in a wide variety of products such as micro-acoustical sensor, gyro-sensor, accelerometer, etc. Most prior art MEMS manufacturing processes are not fully compatible with a standard CMOS process. For example, U.S. Pat. Nos. 5,490,220; 7,190,038; 7,202,101 disclose MEMS manufacturing processes which require special material or equipment that are not provided in a standard CMOS process, and thus it costs more to manufacture MEMS devices thereby. Moreover, it is often required to perform a post treatment process, such as surface micromachining or bulk micromachining, on the manufactured MEMS device to enhance the device performance. There are only few MEMS manufacturing processes that are compatible with a standard CMOS process, such as U.S. Pat. No. 5,970,315. However, this conventional process does not take into consideration how a post treatment process can be integrated therewith. Thus, it is desired to provide a method for making a MEMS device, which is fully compatible with the current CMOS process, and can be easily integrated with MEMS post treatment processes.